Ventilating air discharge muffler



Aug. 30, 1960 J F. STEPHENS VENTILATING AIR DISCHARGE MUFFLER Filed July19, 1956 2 Sheets-Sheet 1 J I 4 /Z 4,.

. 4 4 l/ 150 w l j 44 5 50 g X L la 56 \Tos EPl-l F STEPHENS INVENTOR AORNEY Aug. 30, 1960 J. F. STEPHENS VENTILATING AIR DISCHARGE MUFFLER 2Sheets-Sheet 2 Filed July 19, 1956 United States Patent VENTHJATING AIRDISCHARGE MUFFLER Joseph F. Stephens, Kansas City, Mo., assignor toGustin- Bacon Manufacturin Company, Kansas City, Mo., a corporation ofMissouri Filed July 19, 1956, Ser. No. 598,784 Claims. (Cl. 18142) Myinvention relates to a ventilating air discharge mufller and moreparticularly to an improved ventilating air discharge mufiler whichreduces the noise generated in high velocity ventilating systems andwhich permits ready regulation of the flow of conditioned air throughthe mufller.

In modern air-conditioning, ventilating, and heating installations, highvelocity systems are preferred since they permit use of distributingducts having a small crosssectional area. These high velocity systemsnot only result in considerable savings in duct material owing to theirsmall cross-sectional areas, but also require only a comparatively smallspace within the walls, floors, ceilings, and the like in which they areinstalled. One disadvantage inherent in a high velocity system is thegeneration of noise incident to the passage of the high velocity airthrough the system. This noise is particularly evident at the outletgrilles through which the conditioned air is discharged to the space towhich air is supplied. In the prior art, in order to reduce this noiseit has been the practice to interpose a plenum chamber between the smalldistribution ducts and relatively larger air outlets. In some cases theinteriors of the chambers are lined with sound absorbing material.

In one type of unit employed in the prior art, a perforated metalcylindrical sleeve is secured to the inlet duct. A piston within thesleeve is moved to regulate the amount of air entering the plenumchamber by uncovering the correct number of holes in the perforatedsleeve.

In another unit employed in the prior art, a conical metallic outletfrom the distribution duct is disposed within the plenum chamber. Inthis unit a conical metallic damper is shiftable axially of the conicaldistribution duct outlet to regulate the supply of air. In both theseunits of the prior art the high velocity air entering the plenum chamberfrom the inlet duct first is met by metallic members which readilyconduct sound into the area to which the air is to be supplied.

I have invented a ventilating air discharge muflier in which the highvelocity air entering the plenum chamber from a distribution duct is metwith members entirely composed of sound absorbing material rather thanfirst by metallic elements as in the systems of the prior art. Mymufiier affords ready regulation of the amount of air passing from thedistribution pipe to the area to be supplied.

One object of my invention is to provide a ventilating air dischargemuffler which substantially reduces the noise generated in high velocityair supply systems.

A further object of my invention is to provide a ventilating airdischarge muffier in which high velocity air entering a plenum chamberfrom a distribution duct is met by members composed entirely of soundabsorbing material.

Yet another object of my invention is to provide a ventilating airdischarge mufiler in which the volume of air flowing from a distributionduct to an area to be supplied may readily be regulated.

Patented Aug. 30, 1960,

Other and further objects of my invention will appear from the followingdescription.

In general my invention contemplates the provision of a ventilating airdischarge mufiler including a plenum chamber having an inlet connectedto an air distribution duct and an outlet opening into the area to besupplied With air. I mount a plurality of first baffies having irregularconfigurations in the chamber between the inlet and the outlet. I mounta plurality of second baffles having configurations complementary to theconfigurations of the first bafiles adjacent the first baifies toprovide a plurality of tortuous air passages between the inlet and theoutlet. My mufiler includes means for shifting the first and secondbafiies with respect to each other to regulate the flow of air throughthe passages. My plenum chamber and bafiles are formed of materialhaving good sound absorbing properties and having sutficient structuralstrength to retain the shape into which it is molded. In theaccompanying drawings which form part of the instant specification andwhich are to be read in conjunction therewith and in which likereference numerals are used to indicate like parts in the various views:

Figure 1 is an elevation of one form of my improved ventilating airdischarge muifier.

Figure 2 is a sectional view in perspective of my improved ventilatingair discharge mufller taken along the line 2-2 of Figure 1.

Figure 3 is a sectional view of my improved ventilating air dischargemuffier taken along the line 33 of Figure 2.

v Figure 4 is an elevation of a second form of my improved ventilatingair discharge mufiler.

' Figure 5 is a sectional view of my ventilating air discharge mufilertaken along the line 55 of Figure 4.

More particularly referring now to Figures 1 to 3 of the drawings, mymufiler, indicated generally by the reference character 10, includes abase 12, a top 14 and sides 16 and 18. I provide my mufiler 10 with anend 20 formed with an inlet 22 which may be connected to an airdistribution duct (not shown). In the open end of my mufiler 10 remotefrom end 20 I mount by any convenient means a grating or grille,indicated generally by the reference character 24, through which airpasses into the area to be supplied. Bottom 12, top 14, sides 16 and 18,and end 20 and inlet 22 are formed of sound absorbing material.Preferably I mold these members integrally from the material disclosedin the copending application of Joseph F. Stephens and Glenn W. Kerr,Serial No. 318,856, filed November 5, 1952, now Patent No. 2,778,759,for a Thermal Pipe Insulation. The material comprises glass fibershaving an average diameter of no more than ten microns, impregnated witha synthetic resin in an amount from fifiteen percent to thirtyfivepercent by weight of the finished material and cured under such pressureas to give the material a density of between two pounds per cubic footand five pounds per cubic foot. This material has excellent soundabsorbing properties and has sufficient structural strength to retainthe shape into which it is molded without the use of auxiliarystructural members. Any other appropriate sound absorbing materialhaving sufficient strength to be molded may be employed.

Base 12, top 14, sides 16 and 18, and end 20 enclose a space forming aplenum chamber, indicated generally by the reference character 26 inwhich the high velocity air expands as it emerges from a distributionduct connected to inlet 22. The expansion of the high velocity airreduces the air stream velocity and thus contributes to the reduction ofnoise which otherwise would be incident to the passage of the highvelocity air through: the grille 24.

Within the chamber 26 between the inlet 22 and the outlet grille 24 Imount a plurality of first baifies 28. In the form of my muffler shownin Figures 1 to 3, I employ only two baffles 28 secured to therespective sides 16 and 18 by members 30. It is to be understood thatthe members 36 may be formed integrally with baffles 28 with aserpentine, sinusoidal, or antractuous configuration. My mufllerincludes a plurality of second baflies 32 having similar configurationscomplementary to the configuration of baffles 28. Conveniently, I form apair of adjacent baflies 32 integrally and disposej the assembly innested relationship between a pair of baffles 28. This arrangementprovides tortuous or sinuous paths, indicated generally by the referencecharacter 34, for the passage of air from inlet 22 to grating 24.

1 form baffles 28 together with members 30 from sound absorbingmaterial. Preferably I make these baflies from the material disclosed inthe said copending application. Similarly, bafies 32 are formed of soundabsorbing material. While in Figures 1 to 3 I have shown a number ofbaffles 28 and 32 which afford only two sinuous passages 34 betweeninlet 22 and grating 24, it is to be understood that I may employ a.large number of baffles making up a multiplicity of passages 34. If aplurality of passages are to be provided, I form a number of firstassemblies each including a pair of bai'lies 28 joined by members 36 anda number of second assemblies, each including a pair of baffles 32. Inorder to form the passages 34, I dispose the assemblies includingbafiies 32 in nested relationship between the assemblies including pairsof baffles 28. It will be appreciated that in this manner I may make asmany tortuous or sinuous passages 34 as desired.

I provide means for moving the assembly including baffies 32 axially ofthe chamber 26 to regulate the flow of air through passages 34. Abracket 36 fixed between sides 16 and 18 by any convenient means such asscrews or the like 38 rotatably carries a nut 40 mounted on the bracketby means of a peripheral groove 42. A threaded stud 44 fixed to theassembly including bafiies 32 by a plate or head 46 formed on the studpasses through and threadably engages nut 40. It will be appreciat'edthat when nut 40 is turned, the assembly including bafiles 32 will beshifted with respect to the baffles 28. A suitable opening (not shown)in grille 24 gives access to nut 46. If nut 46 is. turned a sufficientamount, baffles 32 contact baflies 28 and the passages 34 will beclosed. These passages are fully open when baffles 32 are symmetricallydisposed with respect to baffles 28. At its end remote from stud 44 theassembly including baffles 32 carries a guide pin 48 secured to theassembly by means of a plate 50 riveted or otherwise secured to theassembly. Guide pin 48 rides in a hole 52 formed in a bracket 54extending across inlet 22 and secured to end 26 by any convenient meanssuch as screws or rivets 56. The nut 46 may be turned empirically toadjust the baflies 32 to a point of minimum noise, that is, to' tune thearrangement to a position of greatest sound absorption.

It will be seen that this form of my invention first provides a plenumchamber 26 into which high velocity air entering inlet 22 expands. Thisexpansion reduces the air stream velocity to contribute to the reductionof noise which otherwise would be incident to the passage of the highvelocity air through grille 24. This form of my invention provides aplurality of sinuous or tortuous passages 34 which break the air streaminto a number of smaller streams. This action of breaking up the airstream further reduces noise. It is thought that this result flows fromthe conversion of lower frequency sound, which latter is moreefiectively absorbed by sound absorbing material. The sinuous ortortuous nature of the paths 34 presents a very large area of soundabsorbing material. to air traveling along the paths.

As has been explained hereinabove, my mufiler is formed of a materialwhich has sufficient structural strength to retain the shape to which itis molded. If desired I may provide my baffle with a sheath or skin 58formed of a suitable material such as aluminum foil or the like. Thissheath seals the baffle against the escape of air through the bafflewall. It also serves as a vapor barrier to prevent seepage of moisturethrough the bafiie walls.

Referring now to Figures 4 and 5, this form of my muffler, indicatedgenerally by the reference character 60, includes a housing having abase 62, a top 64, respective sides 66 and 68 and an end 76 formed withan inlet 72. The housing, including base 62, top 64,

7 sides 66 and 68, and end 70, forms a plenum chamber,

indicated generally by the reference character 73, into which highvelocity air passes from a distribution duct (not shown). The airexpands and loses velocity in the chamber 73. In the open end of thebattle remote from end 70, I mount a grille or grate, indicatedgenerally by the reference character 74. it will be seen that thehousing of the form of my muffier shown in Figures 4 and 5 is similar inall respects to the form shown in Figures 1 to 3 with the possibleexception of its dimensions.

Within the housing including base 62, top 64, sides 66 and 68, and end76, between the inlet 72 and the grille 74 I mount a plurality of firstbaffles 76 having a zigzag configuration. The baiiles 76 adjacent therespective sides 66 and 68 may be secured to the sides by extensions 76formed integrally with the battles 76. In this form of my invention itwill be seen that a pair of bafiies 76 are disposed substantiallycentrally of the base 62. These baflles are joined by ends 30 to formcentral bafiies 76 as a unitary piece. it will be understood that thebaffles 76 adjacent the sides 66 and 68 are molded as integral pieceswith extensions 73 from the material disclosed in the said copendingapplication. Similarly, the two central baffles 76 may be made integralwith ends 80 of the same material.

I dispose a pair of second baffles 62 joined by ends 84 between thebafile 76 adjacent side 66 and one of the central baflies 76. I disposea second pair of second baffies 82 joined by ends 84 between the baffle76 adjacent side 68 and the other central baffle 7 It will be seen thatall the bafiles 82 have a zigzag configuration complementary to that ofthe baffles 76. This arrange ment provides a plurality of tortuouszigzag paths, indicated generally by the reference characters 66,between the inlet 72 and the outlet grille or grate 74. I construct thisform of my mufiler with means for shifting the assemblies includingbat-fies 62 with respect to the baffies 76 to regulate the flow of airthrough the passages 86 and to tune the assembly to a position ofgreatest sound absorption. A bracket 68 fixed between sides 66 and 68 byany convenient means such as screws or rivets 90 rotatably supports anut 92. Nut )2 threadably engages a stud 94 fixed by any convenientmeans such as welding or the like to a U-shaped bracket 96, therespective legs of which are fixed to the assemblies including baflles82. As nut 92 is turned, the baffles 32 shift relative to the baffles 76to regulate the flow of air through passages 86. An opening (not shown)in grille 74 provides access to nut 92. If nut 92' is turned asufficient number of times, the bafli'es 32 contact the baffles 76 andthe passages 86 are closed. With the bafiies -82 symmetrically disposedwith respect to the baffies 76, the maximum amount of air is permittedto pass through the passages 86. Guide pins 98 secured to the ends ofthe assemblies including bafii'es 82 remote from the bracket 26 ride inopenings in a bracket 100 fixed between sides 66 and 68 by screws orrivets 162. Pins 98 and bracket 1% guide the assemblies includingbaflies 82 in their movement with respect to baffles 76.

It is to be understood that the housing including base 62, top 64, sides66 and 68, and end 70 formed with inlet 72 are made of sound absorbingmaterial. Preferably I employ the material disclosed in the saidcopending application. Similarly, I construct bafiies 76 and extensions78 as well as bafiles 82 and ends 84 from the same material. If desiredI may provide this form of my muffler with a sheath or skin 104 ofaluminum foil or the like. While I have shown only two pairs of zigzagbafiles 82 and corresponding baflies 76 to provide four sinuous paths86, it is to be understood that I may employ as many sets of bafiies asdesired to provide a large number of sinuous paths.

In operation of my ventilating air discharge mufiler, high velocityconditioned air from a distribution duct (not shown) enters the inlet 22or 72 and expands into the plenum chamber 26 or 73. As the air expands,its velocity drops. It is to be noted that in both forms of my inventionair entering the plenum chamber is met substantially entirely by soundabsorbing material. More particularly, it is to be noted that nometallic element with which the air comes into contact in passingthrough the mufi'ier extends from the inlet to the outlet of thehousing. After expanding in plenum chamber 26 or 73, the air is dividedinto a plurality of independent streams and is guided along tortuouspaths toward the duct outlet. In the form of my invention shown inFigures 1 to 3, passages 34 provide sinuous paths for the air. In theform of my invention shown in Figures 4 and 5, passages 86 providezigzag paths for the air. The flow of air through passages 34 in theform of my invention shown in Figures 1 to 3 may readily be regulated byturning the nut 40. Similarly the flow of air through passages 86 in theform of my invention shown in Figures 4 and 5 may be regulated byturning nut 92. Upon emergingfrom the passages 34 or 86, the air flowsthrough the grille 24 or 74 to the area to be supplied.

The construction of my mufiler substantially reduces the noise whichotherwise would be incident to the passage of high velocity air throughan outlet grille. First, expansion of the air into the plenum chamber 26or 73 reduces the air stream velocity to contribute to the reduction ofnoise. Second, the breaking up of the air stream into a plurality ofsmaller streams reduces noise. Further, the sinuous or tortuous natureof the air passages provided eliminates any direct path for sound fromthe duct to the grille. These passages also expose a large surface areaof sound absorbing material to the air in the course of its passagebetween the duct and the grille. Besides this, I may tune thearrangement to a position of minimum noise.

It will be seen that I have accomplished the objects of my invention. Ihave provided a ventilating air discharge mufiler which substantiallyreduces the noise which otherwise would be incident to the passage of ahigh velocity air stream through a grille. My mufiler not onlyaccomplishes this result but also permits regulation of the flow of airthrough the muffler.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of myclaims. It is further obvious that various changes may be made indetails within the scope of my claims without departing from the spiritof my invention. It is therefore to be understood that my invention isnot to be limited to the specific details shown and described.

Having thus described my invention, what I claim is:

1. Apparatus for feeding air from a supply duct to 811 area to besupplied with said air including in combination means forming a plenumchamber having an inlet for admitting air from said duct to said chamberto permit admitted air to expand and having an outlet to said area,means forming a pair of first bafile walls having sinuous surfaceconfigurations, means mounting said first battle wall forming means insaid chamber between said inlet and said outlet, means forming a pair ofsecond baffle walls having surface configurations complementary to theconfigurations of said first bafile wall surf-aces, means mounting saidsecond bafile wall forming means within said chamber with said secondbafile walls adjacent said first baffle walls to define a plurality oftortuous paths between said inlet and said outlet to divide the expandedair into a plurality of streams, means for moving said first bafilewalls relative to said second bafiie walls simultaneously to vary thecross-sectional area of said paths defined by said first and secondbattle walls and means for connecting said moving means to said bafilewall forming means.

2. Apparatus as in claim 5 in which said chamber forming means and saidbafile forming means are formed from a sound absorbing material.

3. Apparatus as in claim 1 in which said chamber forming means and saidbaffle forming means are formed of material made up of glass fibers andimpregnated with resin.

4. Apparatus for feeding air from a duct to an area to be supplied withsaid air including in combination means forming a plenum chamber havingan inlet for admitting air from said duct to said chamber to permitadmitted air to expand and having an outlet to said area, a plurality offirst bafi'les having walls with sinuous surface configurations, meansmounting pairs of said first baflles in spaced relationship in saidchamber between said inlet and said outlet, a plurality of means formingpairs of second bafiies having walls with surface configurationscomplementary to the surface configurations of said first baffles, meansmounting the respective second baffle forming means between the baiflesof said first battle pairs with said second baifie walls adjacent saidfirst bafiie walls to define a plurality of tortuous paths between saidinlet and said outlet for dividing the expanded air into a plurality ofstreams, means for moving said first and second bafiles relative to eachother to vary the cross-sectional areas of the paths defined by theWalls of said baffles and means for connecting said moving means to saidbafiles.

5. Apparatus as in claim 4 in which the respective means forming saidsecond baffles comprise integral members having said second bafile wallsand means for connecting said second bafile forming means for movementas a unit.

References Cited in the file of this patent UNITED STATES PATENTS1,l73,583 Johnston Feb. 29, 1916 1,929,595 MacLeod Oct. 10, 19331,938,798 Bourne Dec. 12, 1933 2,075,316 Tyden Mar. 30, 1937 2,091,918Finck Aug. 31, 1937 2,214,467 Lambert et al. Sept. 10, 1940 2,270,825Parkinson et al Ian. 20, 1942 2,502,020 Olson Mar. 28,- 1950 2,759,556Baruch Aug. 21, 1956 FOREIGN PATENTS 472,605 France Aug. 11, 1914813,127 France Feb. 15, 1937 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION 'Patent Nor 2,950,776 August 30 1960 Joseph F. Stephens It ishereby certified that error appears in the printed specification of theabove numbered patent requiring correction and that the said LettersPatent should read as corrected below.

Column 6, line 20, for the claim reference numeral "5" read 1 Signed andsealed this 4th day of April 1961:.

(SEAL) Att ERNEST W, SWIDER XQQ XXXXQQXK ARTHUR w. CROCKER AttestingOflicer Acting Commissioner of Patents Patent Noa 2,950,776

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 7 August so 1960Joseph F. Stephens It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionand that the said Letters Patent should read as corrected below.

Column 6, line 20 for the claim reference numeral "5"- read 1 Signed andsealed this 4th day of April 1961.

(SEAL) A t ERNEST W. SW IDER WXXXQQMM ARTHUR w. CROCKER AttestingOflicer Acting Commissioner of Patents

